Software Architecture

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Software Architecture
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No silver bullet Frederick P. Brooks, Jr.
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There Is Nothing New Under the SUN.
Ecclesiastes 19-14
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• Architecture???????
• ( Design Pattern????????)
• ??Grady Booch???PPT

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Architecting a dog house
Can be built by one person Requires Minimal
modeling Simple process Simple tools
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Architecting a house
Built most efficiently and timely by a
team Requires Modeling Well-defined
process Power tools
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Modeling a house
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Architecting a high rise
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Early architecture
Progress - Limited knowledge of theory
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Modern architecture
Progress - Advances in materials - Advances
in analysis
Scale - 5 times the span of the Pantheon - 3
times the height of Cheops
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Forces in civil architecture
Kinds of loads - Dead loads - Live loads -
Dynamic loads
Avoiding failure - Safety factors -
Redundancy - Equilibrium
Any time you depart from established practice,
make ten times the effort, ten times the
investigation. Especially on a very large
project. - LeMessuier
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Dimensions of software complexity
Walker Royce
Higher technical complexity - Embedded,
real-time, distributed, fault-tolerant - Custom,
unprecedented, architecture reengineering - High
performance
Higher management complexity - Large scale -
Contractual - Many stake holders - Projects
Lower management complexity - Small scale -
Informal - Single stakeholder - Products
Lower technical complexity - Mostly 4GL, or
component-based - Application reengineering -
Interactive performance
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Forces in Software
Functionality
Cost
Compatibility
The challenge over the next 20 years will not be
speed or cost or performance it will be a
question of complexity. Bill Raduchel, Chief
Strategy Officer, Sun Microsystems
Our enemy is complexity, and its our goal to
kill it. Jan Baan
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The domain of architecting
Wojtek Kozaczynski
The why
The what
System Features
Architecture Qualities
Satisfies
Architecture
S/W Requirements
Constrain
Architecture Representation
System Quality Attributes
Technology
Produces
Defines
The how
The who
Follows
Architect
Process
Skills
Defines role
Organization
Stakeholders
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• The software architecture of a program or
  computing system is the structure or structures
  of the system, which comprise software elements,
  the externally visible properties of those
  elements, and the relationships among them.
• -- Software Architecture in Practice

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• Performance, Security, Availability,
  Functionality, Usability
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• Modifiability, Portability, Reusability,
  Testability

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(Development View)
Scenarios
(Physical View)
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????(Logical View)

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????(Process View)

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????(Implementation View)

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????(Deployment View)

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????(Use Case View)

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• Software Architecture in Practice ?????
• Module
• Decomposition, Uses/Layered, Class/generalization
• Component-and-Connector
• Processes, Concurrency, Shared data,
  Client-Server
• Allocation
• Deployment, Implementation, Work assignment

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• Component, Connector, Port, Role, System,
  Representation, Rep-Map

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• Clements??????????????(Quality Attribute
  Scenarios)????

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• Software Architecture in Practice
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What is a Design Pattern?

• Christopher Alexander
• "Each pattern describes a problem which occurs
  over and over again in our environment, and then
  describes the core of the solution to that
  problem, in such a way that you can use this
  solution a million times over, without ever doing
  it the same way twice" 
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• Eric Gamma, John Vlissides, Richard Helm, Ralph
  Johnson, Design Patterns Elements of ,
  Addison-Wesley 1995. (GoF patterns)
• Frank Buschmann, Regine Meunier, Hans Rohnert,
  Peter Sornmerlad, Michael Stal, Pattern Oriented
  Software Architecture VOL1 A System of Patterns.
  VOL2 Patterns for Concurrent and Networked
  Objects Wiley

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• Gang of Four???
• Creational, Structural, Behavioral
• POSA
• Architectural pattern, Design pattern, Idioms

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• McIlroy 1969??????????????????
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• A software product line (SPL) is a set of
  software-intensive systems that share a common,
  managed set of features satisfying the specific
  needs of a particular market segment or mission
  and that are developed from a common set of core
  assets in a prescribed way.

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• Scientific reasoning is nothing but the result
  of starting from ordinary observations and
  continuing with simple deductions -- only very
  patiently and stubbornly

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• Mary Shaw, David Garlan. Software Architecture
  Perspectives on an Emerging Discipline
• Len Bass, Paul Clements, Rick Kazmand. Software
  Architecture in Practice, Second Edition
• Philippe Kruchten, The 41 View Model of
  Architecture, IEEE Software, 12 (6), November
  1995, IEEE.
• Martin Fowler, David Rice, Matthew Foemmel,
  Edward Hieatt, Robert Mee, Randy Stafford,
  Patterns of Enterprise Application Architecture

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